1. Field
The present invention relates to image processing that is typically performed before character recognition processes, and in particular to systems, devices and methods for detecting and attempting restoration of images with distorted perspective and distorted lines of text.
2. Related Art
Optical character recognition (OCR) is a technology that converts scanned or photographed images with text into machine-editable and searchable text-encoded text.
Photographing a page often results in a distorted perspective or geometric distortion of the page. FIG. 1A shows a distorted photographed image of a single page of a document. For example, distortions can lead to deformation of relative proportions of objects in an image and/or parallelism errors.
Scanning or photographing a document page from a thick bound volume often results in various distortions of the image, e.g., text lines become distorted in areas close to the spine of the book. FIG. 1B shows a scanned image of two pages (double page spread) of a thick book opened near its middle. Geometric distortion or warping near the spine area indicated by reference numeral (110) is visible. This distortion may be caused by book pages not being in uniform intimate contact with the scanning surface or platen surface of a scanner. For example, portions of book pages that are near the spine of the book are usually the portions that are not in intimate contact with the platen surface. Accordingly, distortion occurs in parts of the image corresponding to these portions. These distortions prevent the correct recognition of words located in close proximity to the binding edge of a book.